Dentoalveolar changes observed after the use of customized bonded Shark-Tooth-Like Spurs (JAWs) in adult patients with anterior open bite

ABSTRACT Introduction: Tongue spurs have been successfully used for the early treatment of anterior open bite (AOB). However, according to our knowledge, their effectiveness in the treatment of adults has not been evaluated. Objectives: The purpose of the study was to assess the dentoalveolar changes observed after the use of customized bonded shark-tooth-like spurs (JAWs) in adults with AOB. Methods: Twenty-three adults (22.1±4.4 years) with AOB were selected for the treatment. JAWs made from compomer cement were bonded on the lingual surfaces of the maxillary and mandibular anterior teeth to correct tongue-thrusting. Lateral cephalograms and 3D digital models were obtained to evaluate dentoalveolar features observed before and at three time points after JAWs use. Paired t-test and repeated measure ANOVA tests were used to compare dentoalveolar changes, and Pearson’s correlation was used to analyze the association of dentoalveolar changes and overbite changes. The significance level was set at p<0.05. Results: Significant 3D dentoalveolar changes were observed after the three months of treatment with JAWs. Improvement of overbite (1.0±0.6 mm) and overjet (0.2±0.3 mm), combined with a retroclination of maxillary (3.0±3.0°) and mandibular (2.2±2.7°) incisors, were observed (p<0.05). Moreover, a significant decrease in anterior dental arch width in both maxillary and mandibular arches (0.4±0.4 mm; 0.3±0.3 mm, respectively), and an increase of posterior maxillary (0.1±0.2 mm) dental arch width were observed (p<0.05). These significant changes occurred in the first month after the JAWs use. A significant correlation was found between the initial arch length discrepancy and the amount of overbite correction (r=0.456, p<0.05). Conclusions: Dentoalveolar changes occurred after the first-month therapy with JAWs. The retroclination of the anterior teeth combined with the expansion of posterior teeth suggests a posterosuperior change in the tongue position. These changes were beneficial for the treatment of AOB in adult patients.


INTRODUCTION
Anterior open bite (AOB) is characterized by the open vertical dimension or the presence of negative overbite between the incisal edges of the maxillary and mandibular anterior teeth when the posterior teeth are in occlusion. 1,2 AOB is one of the most challenging malocclusions to be treated due to the high tendency to relapse. 3 The unbalanced neuromuscular functions related to the tongue are considered the main factor associated with AOB. 1,4,5 Consequently, various treatment methods have been proposed to correct the tongue habits, such as the surgical reduction, 6 the use of a tongue elevator, 7 tongue crib, 5,8,9 myofunctional therapy, 10,11 and tongue spurs. 5,[12][13][14][15][16] However, the use of tongue spurs has shown various clinical advantages, since they are simple to insert and can be used in conjunction with fixed orthodontic appliances. 13,14 Tongue spurs were initially described by Rogers 15 for controlling and correcting tongue dysfunction or incorrect posture. Justus 13 has reported that an immediate nociceptive or proprioceptive reflex is established to a new rest posture and swallowing mode after spur use. A continuous biofeedback mechanism, created to inform the patient about the incorrect tongue position, has been reported by Meyer-Marcotty et al. 17 A neurophysiological adaptation process is set after using tongue spurs.
In comparison to spurs, other treatment modalities, such as cribs, are passive restraints, whereas myofunctional treatment controls the false tongue position and function, particularly in conscious patients.
For the early treatment of AOB, several studies have described significant changes resulting from different AOB treatment modalities in children, 3,12,18,19 due to their growth potential.
Cassis et al. 12 evaluated the effects of the spurs with a chin cup in treating patients with AOB in the mixed dentition. Significant dentoalveolar changes that included the increase in dentoalveolar development of the maxillary and mandibular incisors, with correction of the overbite, were observed. Additionally, in isolated spur studies, dentoalveolar changes have been reported. 3,17,20,21 Canuto et al. 3 studied patients with AOB in the mixed dentition during early treatment, and stated that there was increased vertical dentoalveolar development of the maxillary incisors after spur treatment, whether the bonded type or conventional type of spur was employed. Meyer-Marcotty et al. 20 also reported increases in overbite after utilization of the fixed palatal spur appliance, with no significant influence on the inclination of the jaw bases.
Although the use of tongue spurs has been successfully applied for the correction of tongue habits in young patients, with reported dentoalveolar changes, the effectiveness of this therapy in adult patients has never been assessed, as far as we are concerned. Therefore, the present study aimed at evaluating the dentoalveolar effects observed after the use of a customized shark-tooth-like spur (JAWs) made of compomer cement, and bonded on the lingual surfaces of the maxillary and mandibular anterior teeth, to correct the tongue-thrusting habit, thus providing a new tongue position and function to AOB patients. The hypothesis tested was that the use of JAWs would be an alternative approach to correct the tongue-thrusting habit in adult patients with AOB.
Therefore, the purpose of this study was to evaluate the dentoalveolar changes observed after the use of JAWs in adult patients with AOB.

AND IN THE RESTING POSITION
Evaluation of the tongue position during swallowing was performed using indirect retainers coated with molten chocolate before and after the tongue therapy. 22,23 Maxillary and mandibular clear retainers, which were covered with a thin layer of molten chocolate, were placed in the maxillary and mandibular arches.
Then the participants were asked to return their tongue to a resting position and keep their mouth naturally relaxed for swallowing. 24 Tongue-palate contact was revealed. The missing chocolate part was used to indicate the tongue contact (Fig 1).

CEPHALOMETRIC MEASUREMENTS
Lateral cephalometric analyses were conducted at baseline (T0) and three months after tongue therapy with the JAWs (T3). The cephalometric analysis of the dentoalveolar measurements is shown in Figure 3. The Dolphin Imaging Program (v. 11.8 Imaging Program, Chatsworth, California, USA) was used for data collection and generation. interpremolar and, first (6-6) and second (7-7) intermolar widths were measured. In the anteroposterior dimension, the distance between the incisors to a constructed line mesial to the first molars was also assessed using OrthoAnalyzer TM 3D software, 2013 version (3Shape A/S) for the 3D digital dental model analysis (Fig 4).

MEASUREMENT RELIABILITY
To test the measurement reliability, the same investigator repeated the measurement of ten patients after three weeks. The intra-
Significant dentoalveolar changes were observed (Fig 5). Most of the significant dentoalveolar changes occurred within the first month (T1) following the use of JAWs (Tables 1, 2   Values are presented as mean ± standard deviation (SD) or p-value.

DISCUSSION
Several previous studies have reported dentoalveolar changes resulting from various AOB treatment modalities in growing patients, due to the effect of the treatment combined with the growth potential. 3,8,12,18,19,25,26 Furthermore, numerous literature reviews have emphasized that the correction of a functional habit during AOB treatment leads to increased long-term stability. 8,9,13 However, according to our knowledge, only a few case reports on the usage of tongue spurs in adult patients are available, 13 and none of them provided information about the dentoalveolar effects. Therefore, the dentoalveolar changes after tongue therapy in adult AOB patients are unclear.
In the present study, the analysis of dentoalveolar changes fol-  Table 3: Correlation between treatment variables and overbite change.
Pearson's test, r: p-value significant at *p<0.05. previous studies that investigated the effectiveness of tongue reeducation appliances in growing patients during early treatment. 3,19,20 These results suggested that the use of JAWs has the potential to change the tongue-thrusting habit in adult patients, therefore changing the effects of tongue position on dentition.
The mechanism of the spurs therapy in tongue-thrusting has been hypothesized by Meyer-Marcotty et al., 17 according to which neural pathways allow a change in the anterior tongue rest posture through the lingual nerve, (afferent, or sensory), and the hypoglossal nerve (efferent, or motor). 13 Hence, it is inferred that spurs alter orofacial function, theoretically resulting in a change in the dentoalveolar form. 13 Therefore, the use of JAWs might potentially correct the tongue posture and function by stimulating proprioceptive receptors on the pain pathway, then generating the learning process in the brain. Neuromuscular adaptation occurs, then sending the feedback to result in a new normal tongue rest posture, leading to a secondary effect on the dentoalveolar form that allows the spontaneous lingual movement of incisors and canines, thus improving the AOB. 17 The results of the present study suggested that the use of JAWs in adult patients generates similar learning mechanisms in the brain as the ones observed in growing patients, thus allowing for spontaneous dentoalveolar changes. An important finding of the present study was that the most significant dentoalveolar changes occurred in the initial month of therapy with JAWs. This result suggests that an immediately nociceptive reflex is established to a new tongue rest posture and function mode after JAWs insertion, resulting in a physiologic dental drift and dental form changes. 13 Moreover, since no significant dentoalveolar changes were observed during the follow-up periods, we might assume that the nociceptive reflex created by the presence of JAWs can be maintained. Therefore, it might be assumed that the use of JAWs might play an important role in the stability of changes following the treatment of AOB cases. Although various retention periods have been suggested following the use of spurs, little is known about the adequate retention periods for achieving long-term stability. 13,17 According to Justus, 13 spurs should remain in place for at least one year, to ensure that the parafunctional tongue-thrusting habit has been corrected. Haryett et al. 28 also recommended that the spurs should remain for at least six months after the positive anterior overbite is achieved. Moreover, Meyer-Marcotty et al. 17 reported that bite deepening occurred within In the present study, the tongue position during swallowing was assessed indirectly using clear retainers coated with molten chocolate. Although this approach was relatively simple and easy to be performed compared to the conventional palatography using electronic systems, it lacks validation of the accuracy and reliability of the method. This consists in a limitation of the study to correctly identify the tongue posture and function. However, further studies are necessary to assess the accuracy and reproducibility of this method.
Another limitation of the study was the absence of a control group to assess the overall dentoalveolar changes following the use of JAWs. Since only adult patients with non-growth potential were included, the dentoskeletal changes following the use of JAWs were compared with the patients' initial baseline values. In the present study, a positive correlation between the arch length discrepancy and the dentoalveolar changes was observed after the use of JAWs. This result reinforces the potential importance of JAWs for the correction of the tongue position and function in AOB cases. Since the arch length discrepancy in this study was defined as the initial spacing, it is possible to infer that the more severe the AOB, the more benefit from the tongue therapy with JAWs can be achieved. Therefore, the use of JAWs might be considered as an adjunctive treatment modality for the correction of severe AOB cases, such as those requiring surgical correction, to improve the long-term stability of changes. However, the effects of JAWs on the long-term stability of changes following orthodontic treatment should be further investigated.
No correlation was observed between dentoalveolar changes and the initial vertical and anteroposterior skeletal pattern.
However, the size of JAWs for the present study was standardized to 3-mm long for all subjects; therefore, it might have limited their effectiveness in different vertical and anteroposterior skeletal patterns. To date, we found no studies assessing the effects of spur size on the skeletal patterns of AOB. Moreover, most of the commercially available bonding spurs present with the same shape and size to fit all types of problems. 3,12